Removed non-used function HeatCapacityOfWater

This is for issue #19.
This function is not implemented in the MSL and not used in the library.
Reimplemented ConstantPropertyLiquidWater.

This is for #19.
The implementation is completely revised since the compressibility has
been removed.
This simplified the implementation considerably.
We also set u=h in the base properties.
Reformated comment.

This is for #19.
Completely revised PerfectGases package.

This is for #19.
Functions that are not declared in the base class are now made
protected. This is to avoid that models use them, and then become
incompatible with other media models that do not implement these
functions.
The order of functions has been changed to be alphabetically.
MoistAirUnsaturated now contains all implementations, as this is the
medium that is typically used.
MoistAir extends from MoistAirUnsaturated, and only implements what is
different.
Comments have been updated throughout the packages.
Moved IdealGases.SimpleAir to PerfectGases.DryAir

This is for #19.
The reason for moving this medium is to have a consistent naming. Now,
we have MoistAir(Unsaturated) and DryAir, as opposed to
MoistAir(Unsaturated) and SimpleAir.
The medium IdealGases.SimpleAir is also a perfect gas, and all
Media.PerfectGases are ideal gases. Hence, it makes sense to put them
in the same package.
Moved PerfectGases to IdealGases

This is for #19.
Changed T_phX to temperature_phX and h_pTX to specificEnthalpy_pTX

This is for #19.
The reason is that T_phX and h_pTX are not defined in the base class.
The proper name is temperature_phX and specificEnthalpy_pTX.
Renamed PerfectGases to IdealGases.

This is for #19.
Changed icon to be the same as the one from the MSL.

This is for #19
Corrected package.order

This is for #19
Corrected wrong name of the base class.

Thi is for #19.
Reformated and documented code.

This is for #19.
Completely revised GasesPTDecoupled

This is for #19.
Most functions have been copied from the IdealGases package.
Alternatively, they could have been referenced, but the intent was to
make this medium model more self-contained.
Expanded computation of enthalpy in BaseProperties.

This is for #19
Merged code from MSL 3.2.1

This is for #19
Made substanceNames final.

This is for #19
Added comment.

This is for #19
Completely revised GasesConstantDensity/MoistAir{Unsaturated}.mo

This is for #19
Removed final declaration as these variables are assigned in ConservationEquation.mo

This is for #19.
Corrected wrong medium.